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Lighting a Freshwater Planted Aquarium… Properly

  • Marine Depot
  • Nov 20, 2020

It’s no surprise that planted aquariums need good lighting to support plant growth. Aquatic plants use light to drive photosynthesis. The chlorophyll molecules within the plant harvest energy from the sun, but in our case the plants rely on the aquarium light for photosynthesis. Through photosynthesis plants convert light energy to carbohydrates, which are used to fuel new growth. Without proper freshwater lighting, aquatic plants will gradually turn pale and die in a planted aquarium.

Planted aquarium photosynthesis

There are many types of aquarium light fixtures, but not all are suitable for raising freshwater plants. Proper lighting is important because aquatic plants need the right daylight color spectrum for photosynthesis. Technically the plant’s chlorophyll responds strongly to blue and red light, but that kind of lighting wouldn’t look natural on an aquarium. The idea is to have an attractively lit aquarium and promote plant growth. The good news is that there are many types of aquarium lights and fixtures designed for freshwater planted aquariums.

Graph of chlorophyll A & B in relation to light wavelengths and absorbance

Power compact bulbs provide daylight at a 6500K spectrum that is plant-friendly and looks great on tanks full of plants and fish. Unfortunately, there are only a few daylight bulb replacements available these days since the hot trend is to upgrade old-style lighting with super-efficient LED fixtures. The LED fixtures run cooler, are more compact and use much less energy. Many can be also be programmed to accurately reproduce the sun’s daylight spectrum.

A Few Lighting Options:

Planted aquarium lighting options

The AquaMaxx Prism CC is perfect for small planted tanks. It mounts over the aquarium with an adjustable arm. The light even comes with sunrise and sunset programming.

For lighting a larger planted aquarium we like the Kessil A360X Controllable LED for freshwater lighting. The energy-efficient light runs cool and provides natural-looking light and shimmer with a spectrum that has been proven by its users to promote plant growth and enhance coloration. 

Graph of Kessil A360X Light fixture spectrum for planted aquariums

You’ll be able to wirelessly program and control the day length and automatic dimming modes that are pre-programmed into the light.

The Current USA Serene LED system incorporates pre-programmed led lighting above and inside the aquarium that simulates relaxing sunset moods. The kit even includes speakers that play deeply soothing music and effects synced to the lighting!

No matter what size tank you have, there’s a LED fixture that will give your plants the light they need.

Lighting Tips:

  • Start your planted aquarium with about 8 hours of lighting a day. This will give the plants a chance to get established and reduce the chances of stimulating algae blooms. The idea is to have the plants growing and extracting nutrients from the water before increasing the day length. Once your plants start growing you can increase the photoperiod a few more hours if you wish.
  • Some light fixtures have a built-in timer. If yours doesn’t, use a separate digital or analog timer to control the day length.
  • No two planted tanks are the same. You’ll find there are no strict rules for how you light your aquarium, but there are some universal guidelines that have proven success.
  • Don’t use a fixture designed for reef tanks. The spectrum is too heavy in the blue range. Use daylight bulbs or an LED fixture designed for freshwater or planted aquariums. It will be tuned to provide the right spectrum for freshwater plants and make your fish look great too.

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